MKS 777+ with PB MERCURY

  • Hi! I have my new futura with Pb Mercury and MKS 777+ all around. All the servos shake a lot! In all the positions! When I put some force on it it stops! I already flight and no problem, but these seems a lot strange.

  • Difficult to put it on video! When I input the elevator up/down, sometimes one of the servos after go full movement, it goes other side alone, without input from the radio! The ailerons make the same...

  • Hello Norser,


    MKS servo’s are a little sensitive on pulse voltage and incoming power. I tested a lot of servos in the last 12 months including servos from MKS.

    Is the output voltage set to 5,9V or 7,2V??


    Most servo’s have current limiters in the case. If the voltage drops down the current goes up. When you hold the servo’s the current limiter can be active to protect the servo and it will stop.


    Mostly the cable quality and thickness are giving these problems.


    I usually use the Powerbox Servo wiring with 0,5mm2 on red and blue and 0,3mm on white for pulse.


    Voltage drop due to too thin cables can be significant and this is allready a common problem by MKS777 servo's. (If you google MKS777 this is the first thing you find on other forums)


    This does not mean that the servo is bad!!


    These issues can also come from wrong frame-rate settings. The Transmitter is the clock and everything should match that.

    Make sure that the receivers and the mercury are the same. And off course that the setup from the Mercury is on SBus.


    Sometimes a sensor in telemetry can cause these problems also. SBus2 is a bidirectional bus system also. Using SBus, Sbus2 and PWM in the same setup WILL cause problems. Therefor you cannot use SBus and Sbus2 servo’s in the same airplane. I know some crashes due to that.


    Another problem can be interference from another device like fuel-pumps, landing gear spindles and parallel cables without twisting with high currents etc.


    Please do not hesitate to ask for more specific information when needed.


    Best regards,

    John van Gastel